1/4" Security Knob

This is a replacement for e.g. the clamping screw knob of a RAM mount on motorcycles to hinder theft:
When trying to turn, the outer cylinder rotates freely. You need a key-knob to (un)screw it.
It is surely still be possible with a gripper, but not easily by hand while walking along.
I have seen similar commercially available solutions, but wanted to make my own.

In Addition to the printed parts, you also need:
• a bit of glue
• one 1/4-20 hex-nut (height: 7/32" (5,556 mm) / wrench size: 7/16" (11,11 mm))
• a matching washer to protect the plastic

All parts are printable without support.
I have used PETG, seems to hold well for 2 years now.

To assemble:
• a bit of sanding may help to reduce friction later
• take the lower part (with the nut pocket) and insert the nut
• put a bit of glue in the pockets around the nut
• place the outer cylinder over it (flat edge on the inside pointing to the nut)
• put the other inner part (with the "crown") in from above and press the inner parts together

Category: Automotive